<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Title</title>
</head>
<body>

<div id="app">
    <h2 class="title" v-bind:class="['active','line']">{{message}}</h2>
    <h2 class="title" v-bind:class="getClasses()">{{message}}</h2>
</div>

<script src="../js/vue.js"></script>
<script>
    const vue = new Vue({
        el:'#app',
        data:{
            message:'你好呀',
            active:'aaaaa',
            line:'bbbbb'
        },
        methods:{
            getClasses:function () {
              return[this.active,this.line]
            }
        }
    })
</script>

</body>
</html>